PBT Assessment - REACh

PART R11 – PBT ASSESSMENT
(c) Generation of new information
Degradability and chronic toxicity testing of MCSs and UVCBs thought to contain PBT
constituents, is generally not advocated, as the results can often be difficult to assess. For this
reason QSAR estimation and read across are often chosen approaches for generating new
information, other than the testing of strategically selected individual constituents, if needed. With
respect to the order of testing, for the PBT assessment of a mono-constituent substance, this would
generally proceed stepwise with the assessment of potential persistence addressed first, followed by
bioaccumulation (if the P criteria is met) and then toxicity testing (if both P and B are met). For
MCSs and UVCBs this assessment strategy may need to be further evaluated and treated on a case
by case basis, depending upon the ease and cost of generating such data and animal welfare
considerations. Thus for UVCBs and MCS, this process would probably start with a B assessment
including initial assessments of potential for uptake and metabolism (see Section R.11.1.3.2 on
B assessment).
(d) Final assessment
For those substances containing many constituents a case-by-case approach is necessary and only
some general guidance can be given. In relation to the question, “how much information is
required”, a weight of evidence approach should be applied which will include expert judgement
addressing many other issues including feasibility etc.
The further steps in terms of information gathering, and implementation of RMM should be related
to the magnitude of impact to human health and environment (e.g. percentage of PBT/vPvB
impurities, release potential including consideration of the tonnage and the use categories).
An example approach, based on the Hydrocarbon Block approach and the scheme outlined above, is
given in Appendix R. 11-3.
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